We plan to prepare and study the individual bands of protein seen when isoelectric focussing is applied to GSH-Organic Nitrate Reductase (GSH-ONR), GSH-Peroxidase II and GSH-S-Transferase preparations. This makes possible investigations to settle questions which can be settled only with separated and purified individual proteins. Are GSH-ONR, GSH-Peroxidase II, and GSH-S Transferases separate proteins? What are the properties of these separated proteins with respect to substrate specificity, kinetic parameters, identity or non-identity of the 2 subunits, active groups, amino acid composition? What is the difference between Peroxidase II activity of Transferase AA and Transferase A'? Which of the bands catalyze prostaglandin endoperoxidase, hydroperoxidase, isomerase, and reductase reactions? Can antibodies specific to different bands be prepared? Do any of the known inhibitors of GSH-S-Transferases (such as probenecid, bilirubin), possible new inhibitors being prepared with hydrophobic groups added to GSH, or the specific antibodies interfere with organic nitrate metabolism in the liver or with interaction of organic nitrates with smooth muscle? Known correlations between vasodilating potency and rate metabolism by GSH-ONR suggest possible similarity between enzyme and receptor site.